Process for making fortified cellular glass



Patented May 13, .1952

U N -ITED- STATES PATENT OFF-I flBROGESSfFOR MAKING FORTIFIED {GELLULAR .GLAss "Walter 11.; Feta, am Arie-zany, "Pa, assign'or to QPitt'sb'iif'gh "Corning com, Allegheny County, 1' Pa-.,-a-orporation of Pennsylvania efinDrawiljg, ipplicatipxrMamh 21;,11947, :Serial No. 9734,24?

sic tlaims. 015105340 t Waterf Vfifiorht elevated" temperatures" man times .liighly 'cellulated body .of F'glas suitable for use l'a'Sf heatin'sul'ative hifiizeriQLfihdQfdl various Other applications;byiheating a mixture of 'fi'riely'fpulverizeid ass and an agent fde'signedto, give Toff temperaturesnearthe nieltingjoint or j'sinte rig fpoirit "of jthe.fg1ass. The products as Ifihli's di'itaifid were of Iight Weight, ,high resist- TBITGBTO fifle, fiilfi dfmost ccl'i'emi' agencies includji ig water "at 'ofidi'riai y temperatures. .However, the "d'l'lfa'bility of the 31fiaterial With respect to certainefgencies such "as water-fat 'eleva'ted'ltemj'peratures 'Was' not all that might be desired because themlk'ali content of the glass tended-to ieachfout, 1 thus causing disintegration .o'r Tdterio- I ration I of the product. poub'tle's'sithis' actio'nfv'vas ,pionfoted byreasbn of "th'ejhigh pe 16f theprofilic't. The prod'll'tsals .prepa'r edbyj the foregoing irithdds have enjoyed extensive com- "merci'alii'sfe, but some limitations have beniplaced upon the amplication of the materials "Where i'vvater or water vapor at elevated temperatures The present inventionjislbased upon the 'dis- 'covery that "finely I pulverized silica, when iincorporate'd"with'povv'deredfglass, and a assing; agent m anamountrifjabouti'ojto i140'%ba"sed iiponithe iniixtur'e "prior to 'cell1i1ation, has a capacity of 'greatly enhancing 'the resistance of the products obtained bybellulatiri'g the'glass, to the action of water or'mois'ture or similar agencies of deterioration at high temperatures. Exceptionally good results have'been obtainedby the-incorporation of finely pulverized flint in appropriate amounts withthe.pulverized'glass'anol gassing agent. However, the invention contemplates the use of other finely powdered forms of silica such as pulverized 5 sand or .the finely pulverulent mixtures-ofsilica .and glass-constituting the waste sands fromthe grinding and polishing of 'thegla ss iwith'a slu'lry of water and sand as an abrasive agent.

In the practice of the invention practically any from of glass susceptible ofbin'g Sinter'ed when -in 'pulverulent state and bloated with a suitable gassing agentto form cellular-bodies "may be employed. Conventional 'liine soda silica glass is the most comm'on fo'rm and probably the least expensive. othercomponentssuh' ae'pdtassium, 'barium'an'd bofron in appropriatearnounts tofdrm the various conventional "glasses that may 'be available as vcullet may be present. Prereramy thisfgl'a s's will contain a substantiala'riiountof S03 ledmbih'e'dor dissolved). 'Glasse's'of approp'riate'coi'ltefit 'of "S03 are obtaine'dfwhle the glass during the various "melting opefa'tioiisis brought to'aitemperawre' ofapproiiiniately 2500- ZGDO FQah'dhOt 'sllllo'stan'tially'above. At higher trn'p'raltli'ls lthe gl-s's felid's t'o lose its sulfate (content to "an liiidsirable degree and if Heating is "stopped at lower "tem eratures, 'friost grasses will contain? iicssiveambuhtsbf $03. "(51 "ti'imi'm content Tot soajsjeems to be ali l fo'ziim'ate- 1;; 1.13%. 51.1; win "be appreciated that if the YS'u'lfat'e .Eontfit or Itlie fg'lalss is tOOjldW t F'Ihay "be compensatea "in [part by "'Bidditidfis ffiiieh calcium sulfate in "small amount, e. .'g.;.1 "or (2%. Since "the S03 seems to a't pri' army as "an oxy en supplying agent in the reaetio'ns in- "vowing the formation of gases to b'loal't the sin- *teredgeia's's, other Oxygen sup l ing agents "siich as antimon 'triokid'e, ferric oxide, "arsenic tridxid'e or the like imaybe'incorporatedin a p: 'piiate amounts. such amounts usuanyarewithin the rang'e'of .l'to 2'5 7;. p

'Siliafdr' purpos s of increasing 1 the "durability the 'clliilarl'glass'is incorporated in anamount 6f .10 to "40% or 56%. optimum results "with respect to increase of durability are [obtained with percentages of about- 20% an above, the percentage being c-aluciilated upon the basis or tlie compltebatch or pulverized glass and silica. spentisand for-grinding iand'lpolishing plate Iglass 'withasuriy of sand contains about 75.01 80% of .silicaand this. maybe substituted for silica. Cor- 'rectio'n's for the .glass .-content.may be made, "that is, enough may be added tobrin'g 'thes'ilica content within the desiredrange. -Thespent sand Imay be purified of iron andother nonsilicious orglas's constituents or unpurified spent sand -.rnay'b.e employed. Qfcourseit will be dried before use. The fortifying material (silica) is in a heterogeneousmixture with theglass and carbonlof the foafnglass mixture, before Icellu'ation. A'fter celluation, the silica existsfmostlyas imbedded gr msim the cell walls. Therefore, the addition "(ir s ica gwtneglass-cart n imix-results n' "splaeem em of thefg'la' fr "mix. 'The ''fi ebtfo'f this displacement; istof diice the amount" of sulfate normally availablefo'r combining with-the carbon'to g'enei'ate'thelclliiating j'gases; 'henceytliis condition must be oifsteither by increasing thenormal-smfate content of the V of the mass.

3 retained glass, or by mill additions of oxy ensupplying agents in amounts of 0.1% to 0.5%, as hereinbefore set forth.

Preferably the various components of the mixture are very finely powdered, for example so that they will pass a screen of 200 mesh and preferably to an average particle size of microns (2- inches in diameter) or even finer. There is apparently no minimum particle size except of course such as is imposed by the difiiculty and costs of extremely fine grinding.

Best admixture of the various components of the batch is obtained by grinding together glass in the form of cullet, the silica and an appropriate gassing agent. Finely powdered carbon or carbonaceous materials such as carbon black, ground coal or the like is the gassing agent rn'bst commonly employed at the present time. It is employed in amounts within a range of about .1 to 5%. It reacts with certain of the oxides such as the sulfates above mentioned in the glass or with certain oxides that may be added to the batch to form bloating gases in the sintered gla ss mass.

. titles of the mixture are then placed in molds of refractory material such as stainless steel and p are heated to the sintering point of the glass content and preferably somewhat above, e. g.

within a range of about 1400-1600 F. depending somewhat upon the sintering point of the glass." At these temperatures the particles of glass are cohered into a continuous, non-permeable phase of sufficient plasticity to admit of bloating without actual melting and flowing The gassing agents decompose or react with the glass constituents, at the higher I temperatures, to give off gases which are entrapped in the sintered mass and thus produce the desired bloating or cellulation.

Cellulation in the presence of the finely pulverized silica occurs in the substantially the same manner as where silica is not present and the finely pulverized particles of silica seen to be lmbedded in and dispersed in the glass constituting the walls of the cells. Whether there is actual chemical combination to a substantial degree between the silica and the glass components is not as yet definitely established or disproven.

The heating operation involved in cellulating the glass is comparatively slow since the pul- 1 at an appropriate rate is quite satisfactory. At

the completion of the cellulating operation the molds may be stripped from the resultant cellular bodies and the latter may then be annealed. The annealing operation like the cellulating 'to the cell structure.

operation is comparatively slow since the cellular bodies are even poorer conductors of heat than the powders from which they are formed. Usually the annealing operation will require 15 or 25 hours and may be much slower, if the time can be afforded. Annealing of the bodies containing the finely pulverized silica requires much the same conditions as are required in the absence of the finely pulverized silica. Blocks or slabs formed as above described are trimmed to uniform and regular size and are suitable for use as insulative materials or as floats for fish nets, as life rafts and other applications.

The cellulated bodies obtained by application of the invention are of substantially the same properties with respect to tensile strength, crushing strength, workability and such like properties as the conventional cellular glass obtained-without the addition of silica. The cellularity as indicated by the apparent density is high. Usually apparent density is within a range of .14 to .18. The cells are relatively small and uniformily distributed. The resistance to the action of moisture especially at high temperatures is much higher and may be several fold that of conventional materials.

Standarized comparative tests of their resistance to water at elevated temperatures were conducted by placing samples of the materials in an autoclave and subjecting them to the action of water at elevated pressures and temperatures. The resistance to moisture under the standardized conditions was determined by weighting the samples before and after treatment and also by breaking the samples and observing the depth of penetration of moisture in- In preparing standard samples, cylinders of cellular product 4.4 cm. in diameter and 7.7 cm. in length were cut from the slabs or blocks with a core drill. These samples were wet with water, sponged off and weighed. The samples were immersed in water in an autoclave and brought to the temperature corresponding to pounds pressure per square inch for a period of 2 hours. They were then allowed to cool in the autoclave. Subsequently, they were removed, excess water was sponged off and they were again weighed to determine the amount of water taken up. They were also broken and the depth of penetration of water measured in centimeters. Under the conditions described, a similar sample of common cellular glass will take up about '70 to grams of water. Tests were conducted upon samples of cellular glass of various silica contents. These samples were prepared from batches containing .1'7% of carbon black. The results of tests conducted upon laboratory lloatches containing silica are tabulated as folows:

Percentages as herein expressed are by weight.

The resistance to the action of moisture of the materials above described may be 5 or 6 times that of conventional materials.

The forms of the invention herein described are by way of example. It will be evident to those skilled in the art that numerous modifications may be made therein without departure from the spirit of the invention or the scope of the appended claims.

I claim:

1. A process for manufacturing fortified cellular glass resistant to permeation by water at elevated temperature, comprising the steps of providing an intimate mixture of finely pulverized glass, silica and carbon black, in proportions by Weight of .l% to .2% carbon-10% to 40% silica-and the balance glass, heating the mixture in closed molds to a temperature sufiicient to sinter the glass to enclose the silica and carbon black, raising the temperature sufilciently to effect a reaction between the glass and caricon to cellulate the sintered mass, and thereafter annealing the cellulated product.

2. A process for manufacturing fortified celcular glass resistant to permeability by water at elevated temperatures, comprising the steps of providing a finely pulverized intimate mixture in proportions by weight of .1% to .2% carbon 10% to 40% silicaand the remainder lass, heating the mixture in closed molds to sinter the glass, raising the temperature of the sintered mass to cellulate the mass through reaction be tween the glass and carbon to form small substantially uniform closed glass cells impregnated with the silica, removing the cellulated product from the molds, and annealing the product.

3. A process for manufacturing cellular glass having increased resistance to permeability by moisture at elevated temperatures, comprising the steps of providing an intimate mixture of finely pulverized glass, carbon and silica, in proportions by weight of about 80% to 60%0.1% to 0.2 %and 20% to 40%, respectively, heating the mixture in closed molds to a temperature sufi'icient to effect the softening and cohering of the glass particles without substantial chemical reaction between glass, carbon or silica, increasing the temperature of the cohered mass sufficiently to generate cellulating gases through chemical'reaction between the glass and carbon without substantial reaction of the glass or carbon with the entrapped free silica.

WALTER D. FORD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,123,536 Long July 12, 1938 2,233,608 I-Iaux Mar. 4, 1941 2,310,432 Haux Feb. 9, 1943 2,337,672 I-Iaux Dec. 28, 1943 FOREIGN PATENTS Number Country Date 490,168 Great Britain Aug. 10, 1938 

1. A PROCESS FOR MANUFACTURING FORTIFIED CELLULAR GLASS RESISTANT TO PERMEATION BY WATER AT ELEVATED TEMPERATURE, COMPRISING THE STEPS OF PROVIDING AN INTIMATE MIXTURE OF FINELY PULVERIZED GLASS, SILICA AND CARBON BLACK, IN PROPORTIONS BY WEIGHT OF .1% TO .2% CARBON-10% TO 40% SILICA-AND THE BALANCE GLASS, HEATING THE MIXTURE IN CLOSED MOLDS TO A TEMPERATURE SUFFICIENT TO SINTER THE GLASS TO ENCLOSE THE SILICA AND CARBON BLACK, RAISING THE TEMPERATURE SUFFICIENTLY TO EFFECT A REACTION BETWEEN THE GLASS AND CARBON TO CELLULATE THE SINTERED MASS, AND THEREAFTER ANNEALING THE CELLULATED PRODUCT. 